258 Section 2 Foundations and Framing for 500 days, which is more than enough time to enclose the building. OSB panels for flooring are available in thicknesses from 19/32″ to 1 1/8″ with tongue-and-groove edges. OSB should be installed with the long edges running perpendicular to the joists. The boards should be fastened using urethane-based adhesive and with nails or screws spaced every 6 inches on supported panel ends and every 12 inches in the centers of the panels. Fasteners should penetrate the wood joist 1″. All plywood and OSB expands slightly as it absorbs moisture, so a 1/8″ gap should be left between edges and ends of sheets. A 10d box nail makes a good spacer. Most OSB flooring products have self-spacing tongue-and- groove edges, so no additional space is required. Joints should be staggered in successive courses, Figure 10-43. Stiffness is increased significantly when pan- els are glued to the joists in addition to using fasteners. This system ensures squeak-free con- struction, eliminates nail popping, and reduces labor costs. Before each panel is placed, a 3/8″ bead of con- struction adhesive (glue) is applied to the joists, as shown in Figure 10-44. Spread only enough adhe- sive to lay no more than two panels. Two beads of adhesive are applied on joists where panel ends butt together. All screwing or nailing must be completed before the adhesive sets. When laying tongue-and-groove panels, apply adhesive along the groove. Use a 1/8″ bead so that excessive squeeze-out is avoided. The bead can be either continuous or spaced. Drive sheets into the groove of previously laid subflooring by using a maul and a protective piece of scrap lum- ber. See Figure 10-45. Leave a 1/8″ space at all end and edge joints. Immediately fasten the subfloor with screws or nails. Use an autofeed screw gun to work more quickly, Figure 10-46. 10.7.2 Plywood Plywood was once considered the best prod- uct for subflooring. It has been replaced by OSB as the most common subflooring material. Both pro- vide a smooth, even base and acts as a horizontal diaphragm that adds strength to the building. Although 1/2″ plywood over joists spaced 16″ O.C. meets the minimum IRC requirements, 1/8" Space 1/8" Space Along joist 12" Along edge 6" Minimum nailing pattern 5/8" OSB–joist 16" O.C. Goodheart-Willcox Publisher Figure 10-43. Properly installing OSB subfloor. Note the nailing pattern and how joints are staggered for added strength. Copyright Goodheart-Willcox Co., Inc.